1. Field of the Invention
This invention relates to a sheet-like sandwich material provided with a local reinforcement and to a method of providing a local reinforcement in a sheet-like material, such as a sandwich structure. More specifically, the invention relates to a thermoplastic sandwich structure and to a method of providing a reinforcement in a thermoplastic sandwich structure.
2. Description of the Related Art
Sheet-like materials, such as sandwich structures, find wide application in areas where materials are used which must combine a high strength or rigidity with a light weight. This is the case, for example, in air, space, and transport applications.
Sandwich structures generally consist of a core material that is light in weight, with a top layer, often reinforced, on both surfaces thereof. Owing to the excellent bonding between the top layers and the core material, proper stiffness is obtained. The other properties of the material are partly determined by the nature of the various materials.
Known sandwich structures are based on a core material having a honeycomb structure. Another type of sandwich material is described in European Patent Applications Nos. 264 495 and 268 148, which are incorporated herein by reference. This material is fully thermoplastic and consists of a core material including, among other components, a thermoplastic foam, and two top layers consisting of a fibre-reinforced synthetic plastics material, such as polycarbonate or polyether imide.
In European Patent Application No. 88202345.0, which is incorporated herein by reference, a flame-retarding sheet material is described which is also thermoplastic.
European Patent Application No. 345 855, published on Dec. 13, 1989, which is incorporated herein by reference, relates to a non-foamed film which can be used for the manufacture of a thermoplastic sandwich material.
In the application of a sandwich structure, it may sometimes be desirable that local reinforcements be provided in the material. Sandwich structures are often in the form of a plate, for example, a wall panel, to which various objects must be secured. As this may locally involve rather considerable forces, it is necessary to provide local reinforcement to enable auxiliary means to be secured. In the known systems this is effected by making a hole in one of the top layers of the sandwich structure. Subsequently, core material is removed, whereafter a solid filler is substituted for the core removed. Conventional fillers are based on thermosetting two-component systems. This operation is highly labor-intensive, the result of which is that the cost of labor involved in processing sandwich structures is high, and processing takes a long time, too.